Balance re-trainer

ABSTRACT

A balance training apparatus is disclosed for supporting individuals with a reduced ability to maintain balance while standing, comprising means for biasing a user towards an upright position when deviating therefrom in two planes. The apparatus comprises a variable spring system that combines a 2-degrees-of-freedom joint with said biasing means into a single element in a simple and advantageous construction.  
     The apparatus comprises two vertical supportive rods connected to a base by said joints and a bracing for support of the pelvis of a user. The bracing is connected to the upper end of the rods by joints having one degree of freedom. The vertical rods has a lower, elastic part that connects a stiffer, upper part of the rod to the base and constitutes the joint there between as well as constitutes the biasing means.  
     Further is disclosed a balance training apparatus comprising compliant knee supporting means arranged to support the front side of the upper end of the shanks and following the movements of the individual in the said two planes, so as to assisting the knee extensor muscles for retraining purposes.

[0001] The present invention relates to a balance training apparatuswhich is suited for supporting individuals with a reduced ability tomaintain balance while standing for retraining purposes, comprisingmeans for biasing a user towards an upright position when deviatingtherefrom in a frontal plane as well as in a sagittal plane of theindividual. The apparatus comprises a variable spring system thatcombines a 2-degrees-of-freedom joint with said biasing means into asingle element in a simple and advantageous construction.

[0002] The present invention further relates to a balance trainingapparatus comprising compliant knee supporting means arranged to supportthe front side of the upper end of the shanks and following themovements of the individual in the said two planes, so as to assistingthe knee extensor muscles for retraining purposes.

INTRODUCTION

[0003] Standing-balance training is a crucial therapeutic procedure inrehabilitation of neurologically impaired individuals. Modem concepts ofneurological rehabilitation favour task-oriented therapy, where oneneeds to practice balancing in order to re-learn to balance.

[0004] Various neuromuscular disorders reduce the ability of an impairedindividual to effectively maintain balance while standing. Impairedindividuals can be divided into two groups according to their residualbalancing abilities. The first group is comprised of subjects withdiminished ability (e.g. hemiparesis, paraparesis and tetraparesis),while the second group is characterised by severe impairment(hemiplegia) or complete loss of balancing abilities (paraplegia andtetraplegia).

[0005] The goal of neurological rehabilitation for the group ofindividuals with diminished balancing abilities is to retrain theresidual peripheral and central nervous system in order to developalternative movement strategies needed to co-ordinate motor behaviour asefficiently as possible within the constraints posed by the injury.Different methods facilitating the balance re-learning process have beendeveloped. The common techniques include the use of oscillatory platformmovements while the impaired individual is standing on the platform, orto provide biofeedback on weight distribution. Both methods aim toimprove balancing abilities in impaired individuals. However, thesemethods should be applied with caution as the subjects are exposed tosituations of destabilisation. There is an inherent problem ofprotecting the subject from falling, which must be solved to ensuresafety. Unfortunately, safety implementations in turn pose a significantlimitation to the outcome of a training process.

[0006] Such methods cannot be applied to the group of severely impairedindividuals since they are unable to stand without assistance.Consequently, they are often confined to a sitting position, which canresult in various medical complications requiring prolonged andexpensive professional medical treatment. A common therapy method forthe second group is passive standing in rigid standing frames or tilttables. These therapies are rather static and hence an unattractiveactivity since they do not require a sufficient degree of cognitiveinvolvement.

[0007] A known device, disclosed in Matja{haeck over (c)}ić and Sinkjær:A Mechanical Apparatus for Arm-Free Therapeutical Paraplegic Standing,Proc. of the International Biomechanics Workshop, April 1999, Enchede,The Nederlands and in Matja{haeck over (c)}ić, Sinkjær and Johannesen:Unsupported Standing after Spinal Cord Injury, Proc. of the 4th AnnualConference of the International Functional Electrical StimulationSociety, August 1999, Sendai, Japan provides an impaired individual witha fall-safe balancing environment, where the balancing efforts of astanding individual are augmented by stabilising forces acting at thelevel of the pelvis in the sagittal and frontal planes of motion,assisting the balancing activity of ankle muscles (sagittal plane) andankle and hip muscles (frontal plane). The biasing means disclosedcomprises two hydraulic motors which may be used for actively biasing auser in a given direction or may be used for providing a resilienteffect, described as being equivalent to a passive spring effect.However, a system of hydraulic motors is expensive to produce, complexto operate and requires frequent maintenance to function properly.Moreover, such system is rather space consuming and is all in all onlysuited for experimental purposes in a scientific context and is notsuited for use in rehabilitation training in clinics and in particularnot suited for use at home of the individuals in need of training.

[0008] Another device, more remote from the present invention, isdisclosed in Godall et al.: Enhancing postural stability in hemiplegicusing externally applied forces, Int. Journal of Rehabilitation, 1985and in Wing, Allison and Jenner: Retraining and retaining balance afterstroke, Baillière's Clinical Neurology, Vol. 2, No. 1, April 1993, inwhich the individual is supported by a belt at the hip level on whichtwo actuators act in a horizontal plane in perpendicular directions sothat the individual may be supported and at the same time purposely bepushed or disturbed for training and evaluation purposes. This devicehas the same drawbacks as the above-discussed and is intended mainly forscientific purposes.

[0009] It is thus an object of the present invention to provide abalance training apparatus which is suited for supporting individualswith a reduced ability to maintain balance while standing for retrainingpurposes, comprising means for biasing a user towards an uprightposition when deviating therefrom in a frontal plane as well as in asagittal plane of the individual in which the biasing means are ofsimple, inexpensive construction.

[0010] During use of the device, it may be necessary to keep the kneesof the user, the standing individual, extended if the individual is notable to do so on its own. This is with the above-discussed prior artobtained by means of stiff plastic braces. An alternative piece ofequipment is a transverse, stiff beam connecting the two vertical rodsof a similar device and supporting the individuals on the front belowthe knees so as to keep the knees in full extension as disclosed inMatja{haeck over (c)}ić and Bajd: Arm-Free Paraplegic Standing—Part II:Experimental Results, IEEE Trans. on Rehabilitation Eng., Vol. 6, No. 2,June 1998. The training of the function of the muscles controlling theknees has, with the known devices, to be performed with other means. Ithas been found that a surprisingly improvement of the balance trainingcan be obtained by supporting the individuals knees in an extendedposition in a compliant manner by means of supporting means arranged tosupport the front side of both legs of the individual near an upper endof the shanks, when the knee supporting means is arranged to follow themovements of the user in the frontal plane as well as in the sagittalplane. Thereby, the individual may during the balance training enhancethe training of the balance about the vertical postural axis whichmainly is controlled by the knee joints.

[0011] Feedback systems for providing the individual with informationabout its inclination from vertical is known, e.g. from theabove-mentioned Matja{haeck over (c)}ić and Bajd: Arm-Free ParaplegicStanding—Part II: Experimental Results, IEEE Trans. on RehabilitationEng., Vol. 6, No. 2, June 1998, in which an audio signal is providedindicating the inclination in the sagittal plane and a visual feedbacksystem indicating the inclination in both planes for training purposesis disclosed in Nichols: Balance Retraining After Stroke Using ForcePlatform Biofeedback, Physical Therapy, Vol. 77, No. 5, May 1997. Thetraining program disclosed in the latter article is intended for usewith a force platform on which the individual to be trained is standingbut such computer programs may as well be used with the apparatus of thepresent invention. A preferred computer training system is disclosedbelow in which a number of improvements are included, in particular theintroduction of a “dead zone”, a range of inclination around thevertical position in which the cursor on the visual output screenpresented to the individual does not move, such that the individual isforced to move to higher inclinations than the dead zone to activate thecomputer and to use the training apparatus e.g. as a computer pointingdevice.

BRIEF DESCRIPTION OF THE INVENTION

[0012] The above object of the invention is reached by integrating thejoint between the base and the vertical rod and the biasing means forkeeping the user from falling. Thus the present invention relates to abalance training apparatus comprising

[0013] two vertical supportive rods, each connected at a lower end to abase by a joint having two degrees of freedom,

[0014] a bracing means suitable for supporting the pelvis of a userstanding between the two vertical supporting rods, the bracing meansbeing connected to an upper end of each of the vertical supportive rodsby a joint having one degree of freedom allowing mutual movement betweenthe bracing means and the vertical rods in the plane of the two verticalrods,

[0015] biasing means for biasing the user towards an upright positionwhen deviating therefrom in a frontal plane as well as in a sagittalplane of the user, wherein at least one of the vertical rods has alower, elastic part connecting a stiffer, upper part of the rod to thebase and constituting the joint there between as well as constitutingthe biasing means, and the apparatus further comprises

[0016] adjustment means for adjusting the stiffness of the lower,elastic part.

[0017] It is obtained by integrating the joint and biasing means byemploying an elastic part of at least one of the vertical rods that theconstruction is simplified and readily can be made inexpensive and withlow maintenance requirements. It is sufficient that one of the rods hasthe elastic part, but it is for reasons of symmetry of forces preferredthat each of the two vertical rods has a lower, elastic part connectinga stiffer, upper part of the rod to the base and constituting the jointthere between as well as constituting the biasing means.

[0018] The elastic part may be manufactured from e.g. natural orsynthetic rubber, from flat springs being arranged with perpendicularaxis of resilience on the two rods, etc., but it has been found that itis most suitable that the elastic part is constituted by a vertical,helical spring which is largely maintenance-free, inexpensive and can befound off-the-shelf with suitable elastic properties.

[0019] It is also preferred that the apparatus further compriseslimitators for limiting the angle of inclination from vertical for eachof the vertical rods so that the users do not risk to reach too extremepositions and that the whole apparatus will not tip over as a resultthereof.

[0020] A preferred way of adjusting the stiffness of the lower, elasticpart is to employ adjustment means that may adjust the effective lengthof the lower, elastic parts. This may be achieved e.g. by displacing arod vertically inside a helical spring constituting the elastic part,but it is preferred that the adjustment means for each vertical rodcomprises an outer mantle arranged around the elastic part with aninner, vertical surface of the mantle fitting around the outer side ofthe elastic part, the mantle being vertically displaceable such that theeffective length of the elastic part is adjusted thereby. The limitatorsmay for such arrangement preferably be connected to the mantles so thatthey are displaced together therewith and define circular openingsthrough which the vertical rods pass.

[0021] It is furthermore advantageous that the apparatus compriseslocking means for temporarily locking each of the vertical rods in avertical position for use when users are entering or leaving theapparatus and for locking the rods when the stiffness of the elasticpart is adjusted. The locking means may be connected to theabove-described mantle and be displaced together therewith.

[0022] It is, for the support of users that do not possess the abilityto keep the knees extended, an advantage that the apparatus furthercomprises knee supporting means arranged to support the front side ofboth legs of the user near an upper end of the shanks, the kneesupporting means being arranged to follow the movements of the user inthe frontal plane as well as in the sagittal plane. It is furthermorefor knee training purposes as discussed above an advantage that the kneesupport means are compliant. It is yet further an advantage that thecompliance of the knee supporting means is adjustable.

[0023] It is also preferred that the apparatus comprises sensor meansfor measuring the inclination of in the frontal plane as well as in thesagittal plane of the vertical rods and producing an output accordinglyso that an evaluation and/or a feed back system may be established.

[0024] The invention relates in a further aspect to a balance trainingapparatus comprising

[0025] two vertical supportive rods, each connected at a lower end to abase by a joint having two degrees of freedom,

[0026] a bracing means suitable for supporting the pelvis of a userstanding between the two vertical supporting rods, the bracing meansbeing connected to an upper end of each of the vertical supportive rodsby a joint having one degree of freedom allowing mutual movement betweenthe bracing means and the vertical rods in the plane of the verticalrods,

[0027] biasing means for biasing a user towards an upright position whendeviating therefrom in a frontal plane as well as in a sagittal plane ofthe user, wherein the apparatus further comprises compliant kneesupporting means arranged to support the front side of both legs of theuser near an upper end of the shins, the knee supporting means beingarranged to follow the movements of the user in the frontal plane aswell as in the sagittal plane.

BRIEF DESCRIPTION OF THE FIGURES

[0028] A preferred embodiment of the present invention is illustratedwith the accompanying figures of which

[0029]FIG. 1 is a perspective view of the apparatus complete with thebase plate and an individual situated in the apparatus,

[0030]FIG. 2 shows the apparatus of FIG. 1 as seen from the side, inwhich the individual is inclining forward in the sagittal plane,

[0031]FIG. 3 shows the apparatus of FIG. 1 as seen from the front, inwhich the individual is inclining in the frontal plane,

[0032]FIG. 4 shows the apparatus of FIG. 1 as seen from the side, inwhich the individual is inclining forward in the sagittal plane andconcurrently is flexing the knees, whereby the knee support comes intoaction,

[0033]FIG. 5 shows the lower part of a vertical rod as seen from theside with the locking means in a locked position,

[0034]FIG. 6 shows the locking means of FIG. 5 as seen from above,

[0035]FIG. 7 shows the lower part of a vertical rod as seen from theside with the locking means in an unlocked position and the upper partof the rod in an inclined position,

[0036]FIG. 8 shows the locking means of FIG. 7 as seen from above,

[0037]FIG. 9 shows a vertical section of the lower part of a verticalrod as seen from the side with the locking means in a locked position,

[0038]FIG. 10 shows a vertical section of the lower part of a verticalrod as seen from the side with the locking means in an unlocked positionand the upper part of the rod in an inclined position,

[0039]FIG. 11 shows a vertical section as in FIG. 10 wherein theadjustment cylinder is adjusted upwardly to provide a higher stiffness,

[0040]FIG. 12 shows a vertical section in the sagittal plane of thelower part of a vertical rod disclosing the inclination sensor for thefrontal plane,

[0041]FIG. 13 shows the section of FIG. 12 in which the upper part ofthe rod is inclined in the sagittal plane,

[0042]FIG. 14 shows a vertical section in the frontal plane of the lowerpart of a vertical rod disclosing the inclination sensor for the frontalplane, in which the upper part of the rod is inclined in the frontalplane,

[0043]FIG. 15 is a schematic representation of the linking of thesensors and the personal computer,

[0044]FIG. 16 are diagrams of the dead zone and the mouse velocities asfunction of the inclination in the frontal and sagittal planes for usewith computer training, and

[0045]FIG. 17 A-D shows four screen pictures of the computer trainingprogram.

DETAILED DESCRIPTION OF EMBODIMENT

[0046] The preferred embodiment of the present invention disclosedherein provides an impaired individual with a fall-safe balancingenvironment, where the balancing efforts of a standing individual areaugmented by stabilising forces acting at the level of pelvis in thesagittal and frontal planes of motion, assisting the balancing activityof ankle muscles (sagittal plane) and ankle and hip muscles (frontalplane) and at the level of shanks, assisting the knee extensor muscles.The level of supporting forces can be varied from zero up to the levelwhere no balancing activity is needed from the standing subject.Additionally, movement in the sagittal and frontal planes, acquired bytransducers, is fed to an electronic interface which transforms thecurrent inclinations into computer mouse, joystick or similar pointingdevice signals which are interfaced to a personal computer (PC). Thus, astanding subject, by voluntarily changing the posture in the sagittaland frontal planes, can control various software applications running onthe PC. Further, an advanced balance training and evaluation program isdescribed, which is designed to facilitate and test balancing in thewhole range of anterio-posterior and medio-lateral postural space in agradual and systematic way, thus enabling uniform neuro-rehabilitationprogram and objective evaluation of balancing abilities of a standingsubject.

[0047]FIG. 1 shows a schematic drawing of the apparatus 1 and anindividual 2 standing in it. The apparatus consists of the base plate 3,two 2-degrees-of-freedom variable spring systems 4 with an adjustablestiffness of 0 to e.g. 15 Nm/degree, two 1-degree-of-freedom joints 5,two vertical supportive rods 6 of adjustable heights, a size adjustablebracing system 7, a stiffness adjustable compliant band 8, a heel stop 9and two movement limitators 10. Both 2-degrees-of-freedom variablespring systems 4, having adjustable stiffness, are mounted to the baseplate 3 and are linked to 1-degree-of-freedom joints 5 by verticalsupportive rods 6. A person 2 is standing on the plate 3 with heelsplaced in front of the heel stop 9, having the pelvis supported by thebracing system 7 and shanks supported by the adjustable compliant band8. The apparatus 1 has the following three degrees of freedom as shownin FIGS. 2-4:

[0048] 1. The inclination in the sagittal plane as illustrated in FIG.2, in which the inclination is mechanically limited to, e.g., ±15degrees by means of movement limitators.

[0049] 2. The inclination in the frontal plane as illustrated in FIG. 3,in which the inclination is mechanically limited to, e.g., ±15 degreesby means of movement limitators.

[0050] 3. The knee flexion as illustrated in FIG. 4, in which theinclination is mechanically limited to, e.g., 15 degrees by means of aslack stiff wires incorporated in the adjustable compliant band.

[0051] The variable spring system 4 and the features and functions areshown in details in FIGS. 5-14. FIG. 5 shows the lower part of avertical rod with the 2-degrees-of-freedom variable spring system 4 asseen from the side. It consists of a base cylinder 11 connected to thebase plate 3, a helical spring 12 connected at the lower end to the baseplate 3 and at the upper end to a stiff part 13 of the vertical rod 6,an adjustment cylinder 14 which is an outer mantle around the spring 12with an inner surface fitting to the outer side of the spring 12. Theadjustment cylinder 14 is in threaded engagement with the base cylinder11 and may be displaced vertically by turning. On top of the adjustmentcylinder 14 is a distance piece 15 to create a vertical distance betweenthe upper rim 16 of the adjustment cylinder 14, above which rim 16 thespring 12 may bend, and the limitator 10 that has a circular opening 17through which the stiff part 13 of the vertical rod 6 passes. A pair oflock plates 18 is hinged to the limitator 10 and may be switched betweena locked position as shown in FIGS. 5 and 6 in which the twosemi-circular openings in the plates 18 lock the rod 6 in asubstantially vertical position, and an unlocked position as shown inFIGS. 7 and 8 in which the lock plates 18 are turned away from the rod 6and allow it to assume an inclined position.

[0052] By rotating the adjustment cylinder 14, the free, effectivelength of the spring 12 may be varied, thus varying also the mechanicalstiffness of 2-degrees-of-freedom variable spring system 4. Thus, thevariable spring system 4 disclosed herein combines a2-degrees-of-freedom joint and biasing means for biasing a user 2towards an upright position when deviating therefrom in a frontal planeas well as in a sagittal plane of the user 2 into a single element,which is of low cost, easy to produce and practically maintenance-freeand which is highly compact. Other functions, such as the limitators 10for limiting the inclination of the vertical rods 6 and the lockingmechanism 18, are easily integrated in the disclosed variable springsystem 4. The locking mechanism consisting of the two, hinged lockplates 18 is used for stabilising the training apparatus 1 when e.g. anindividual 2 enters or leaves the apparatus 1 or when the stiffness ofthe spring system 4 is adjusted by turning the adjustment cylinder 14.

[0053] Vertical sections of the variable spring system 4 are shown inFIGS. 9-11, in which the bending of the spring 12 and the effect of thevertical displacement of the adjustment cylinder 14 is demonstrated. Avertical section of the lower part of a vertical rod 6 as seen from theside is shown in FIG. 9 with the locking means 18 in a locked positionand in FIG. 10 with the locking means 18 in an unlocked position and thestiff, upper part 13 of the rod 6 in an inclined position. The lowerpart of the spring 12 is supported on the outer side by the inner sideof the adjustment cylinder 14 such that the spring 12 only bends fromthe vertical level of the upper rim 16 of the adjustment cylinder 14.Thus, the effective length of the spring 12 is reduced, therebyincreasing the stiffness of the variable spring system 4 in the positionof the adjustment cylinder 14 shown in FIG. 11 as compared to theposition shown in FIG. 10 due to the higher vertical position of theupper rim 16.

[0054] The current angles of inclination of the vertical rods 6 aremeasured with two transducers which provides an output for the angle ofinclination in the sagittal and the frontal plane, respectively. Atransducer that has been developed for the purpose and arranged formeasuring the inclination in the frontal plane is shown in FIGS. 12-14of which FIGS. 12 and 13 are sections in the sagittal plane and FIG. 14shows a section in the frontal plane. The transducer comprises a slider19 that is arranged in an opening in the stiff, upper part 13 of thevertical rod 6, the slider 19 being slidabe in the longitudinaldirection of the upper part 13 so as to compensate for the change indistance between the upper part 13 during change in angle ofinclination, and a variable resistor 20, a trim potentiometer, mountedon the base cylinder 11 or the base plate 3. The slider 19 and thevariable resistor 20 are connected with a thin-plate rod 21 being muchwider in the frontal plane than in the sagittal plane so that the rod 21will bend as a result of inclination in the sagittal plane, as shown inFIG. 13, whereas an inclination in the frontal plane will result in arotation of the pin of the variable resistor 20 and thus a change of itsresistance which may be provided as an output being indicative of theangle of inclination in the frontal plane. A similar transducer isprovided at the other vertical rod 6 for measuring the angle ofinclination in the sagittal plane.

[0055] The signals from the transducers are led to an electronicinterface that transforms both angles of inclination of the apparatusinto the computer mouse and/or joystick signals, connected to the mouseport and/or the game port of the personal computer, which isschematically represented in FIG. 15.

[0056] The function of the interface is depicted in two plots of FIG.16. In the left plot the middle, square area denotes a dead zone in bothinclination angles where no changes are signalled to the computer. Thisis equivalent to the output of the computer mouse, which is not changingthe position or to the state of the joystick when held in a neutralposition. A person, standing in the apparatus, is faced with the screenof a PC as shown in FIG. 1. For moving the cursor on the screen in thedesired direction the subject has to change posture in either sagittal,frontal or both planes simultaneously. If the dead zone is set to, forexample ±5 degrees in both planes of motion, the subject will beperforming ankle and hip movement in a range of at least ±5 degreeswhile trying to move the cursor on the screen or while trying to changethe state of the joystick. On the right plot a possible relationshipbetween the current angle of inclination in each plane and the speed ofmoving cursor on the computer screen is shown. As long as the dead zoneis not exceeded the output from the interface does not change. Theamount of angle exceeding the dead zone is manifested in a linearincrease of the cursor speed, however other relationship can beimplemented. The mouse buttons can be mounted to the bracing systemwithin the reach of the standing subject.

[0057] By interfacing the apparatus with the PC we substitute the mouseand the joystick, which are predominant inputs in a majority of computerapplications. In this way a standing subject exercises beneficialmovement and balance training 1) through use of the advanced balancetraining and evaluation program software described below, 2) by playinghis/her favourite computer game, and/or 3) by working with othercomputer applications. By doing that a standing subject perturbs andrestores his equilibrium by which inherently re-trains the residualcentral and peripheral nervous system and develops alternative balancestrategies.

[0058] With an adequate choice of supporting stiffness provided by thevariable spring systems a large portion of the population being affectedby various disabilities, preventing them to stand without aid, would beable to re-train their balance abilities.

[0059] Advanced balance training and evaluation program

[0060] Another advantageous component that may be used with theapparatus of the invention as well as with other similar trainingdevices is an advanced balance training and evaluation computer program,which provide means 1) to set-up balance training program for individualperson and 2) to objectively evaluate particular subject's balancingabilities. An objective evaluation is necessary to provide subjects andtherapists with feedback on the improvement of their balancing abilitiesresulting from daily exercise in the apparatus. An example of computersoftware algorithm for balance training and evaluation of neurologicalimpaired subjects while standing in the apparatus at given levels ofsupport provided by the variable spring system and given dead zonesimplemented through electronic interface as described above is givenbelow.

[0061] FIGS. 17A-D shows four screen pictures of the computer trainingprogram. The first scene appearing on the computer screen is shown inFIG. 17A. In the middle of the computer screen an object, which in thiscase has a form of a circle (but could be of another shape), appears. Wename this circle a tracker. Around the tracker eight additional circlesare drawn in such a way to form a symmetrical object, which elements areequidistant to the tracker. Each circle from this symmetrical object istermed as a target. The number of targets can be different from eight,which we use in illustrative example. All the targets are of the samesize (in case of circles the same diameter), while the tracker size (incase of a circle the diameter) can vary. For example it can be 10%, 30%,50%, 70% and 90% of the targets size, thus, representing five differentdifficulty levels. The objective of the standing subject is to bring thetracker into one of the selected targets and keep it there for a periodof time. This is termed as a tracking attempt. The algorithm can besummarised in the following successive steps:

[0062] step 1 (FIG. 17B): The first task for a standing subject is tomove the mouse cursor into the area occupied by the tracker. The size ofthe tracker at this point is the same as the one of the targets. Oncethe mouse cursor is brought in that area a tracking attempt is initiatedand the tracker becomes locked to the mouse cursor, i.e. thereafter, itmoves as the mouse cursor moves.

[0063] step 2 (FIG. 17C): When the tracker is locked to the mousecursor, one of the targets, selected randomly, becomes active and startsto blink, e.g. changes colour between the two pre-determined colours,depicted as to bold in FIG. 17C). At the same time the size of thetracker is changed to the one pre-specified difficulty level before theinitiation of the session.

[0064] step 3 (FIG. 17D): The second task is then to move the trackerinto the active target in such a way that the whole area of the trackeris held in the area occupied by the active target for at leastone-second. The time given at the subject's disposal for completingtracking attempt can be varied. As an example, we define two timeintervals of different duration and we term them as slow and fast, forexample 5 and 10 seconds, respectively. If the task of placing thetracker into the target and holding it there for given period is donebefore the specified time interval elapses then the tracking attempt isconsidered as successfully completed and this is signalled to thesubject, e.g. by a high frequency sound beep. If on the other hand timeinterval elapses and the subject was not successful, this is alsosignalled, e.g. by a low frequency sound beep. The described signallingcould take any other appropriate form.

[0065] step 4 (FIG. 17A): After either subject successfully completesthe task or the selected time interval is elapsed tracking attempt isfinished and the tracker is unlocked from the mouse cursor, re-sized tohave the same diameter as target circles and positioned back to thecentre of the computer screen while the outcome of tracking attempt isstored in the computers memory.

[0066] step 5: The algorithm is idle and waits until the standingsubject chooses to initiate another tracking attempt by undertaking step1 again.

[0067] The above five steps are repeated for a given number ofrepetitions constituting a trial. For example if each target(representing eight directions of movement) is repeated five times (inrandom order, which is unknown to the standing subject) then total offorty tracking attempts are undertaken within each trial.

[0068] When the trial is completed the score percentage is calculatedfor each of the eight targets. The score percentage is then used tograde the performance of the subject. For example a mean scorepercentage value calculated from score percentages from all individualstargets could be presented to the subject. Additionally, a more complexevaluation of the trial results is presented on the screen of the PC ina suitable way. For example at each target location a bar composed ofe.g. five elements if five repetitions were utilised in a trial for eachtarget, could appear. According to the number of successfully completedtracking attempts a corresponding number of bar elements would beilluminated. Additionally, another bar showing the results of the mostsuccessful trial (judged according to e.g. the mean percentage score) atthe same conditions (variable spring system, dead zone, difficulty leveland time interval) performed by the same subject in previous trainingsessions would be displayed. This comparison would visually show theimprovement or decline in subject's balancing performance. Anotherindication of improvement will be obvious from changed trial conditions(variable spring system, dead zone, difficulty level and time interval).The improvement will be shown by decreased support of variable springsystem, increased dead zone (increased postural space), increaseddifficulty level (increased precision of fine regulation of desiredposture) and decreased time interval (increased speed of posturalresponse). The above description of scoring system is just an example.Other scorings of a trial could be utilised.

[0069] The key idea about the proposed algorithm for training andevaluation of balancing abilities is to provide an uniformneuro-rehabilitation program, which allows for direct comparison ofbalancing abilities of a particular subject between different trials aswell as direct comparison between different trials performed bydifferent subjects. The improvement in balancing abilities can bedirectly observed from decreased/increased parameters (variable springsystem, dead zone, difficulty level and time interval).

[0070] It is clear from the above that the usage of the device is notconfined only to neurologically impaired but is also suitable forbalance training in sport, etc.

1. A balance training apparatus (1) comprising two vertical supportiverods (6), each connected at a lower end to a base (3) by a joint (4)having two degrees of freedom, a bracing means (7) suitable forsupporting the pelvis of a user (2) standing between the two verticalsupporting rods (6), the bracing means (7) being connected to an upperend of each of the vertical supportive rods (6) by a joint (5) havingone degree of freedom allowing mutual movement between the bracing means(7) and the vertical rods (6) in the plane of the two vertical rods (6),biasing means (12) for biasing the user (2) towards an upright positionwhen deviating therefrom in a frontal plane as well as in a sagittalplane of the user (2), characterised in that at least one of thevertical rods (6) has a lower, elastic part (12) connecting a stiffer,upper part (13) of the rod (6) to the base (3) and constituting thejoint (4) there between as well as constituting the biasing means (12),and that the apparatus further comprises adjustment means (14) foradjusting the stiffness of the lower, elastic part (12).
 2. An apparatusaccording to claim 1, wherein each of the two vertical rods (6) has alower, elastic part (12) connecting a stiffer, upper part (13) of therod (6) to the base (3) and constituting the joint (4) there between aswell as constituting the biasing means (12).
 3. An apparatus accordingto claim 1 or 2, wherein the elastic part is constituted by a vertical,helical spring (12).
 4. An apparatus according to any of claims 1-3,further comprising limitators (10) for limiting the angle of inclinationfrom vertical for each of the vertical rods (6).
 5. An apparatusaccording to any of claims 1-4, wherein the adjustment means (14) mayadjust the stiffness of the lower, elastic part (12) by adjusting theeffective length thereof.
 6. An apparatus according to claim 5, whereinthe adjustment means (14) for each vertical rod (6) comprises an outermantle (14) arranged around the elastic part (12) with an inner,vertical surface of the mantle (14) fitting around the outer side of theelastic part (12), the mantle (14) being vertically displaceable suchthat the effective length of the elastic part (12) is adjusted thereby.7. An apparatus according to claim 6, wherein the limitators (10) definecircular openings (17) through which the vertical rods (6) pass, andwherein the limitators (10) are connected to the mantles (14) and aredisplaced together therewith.
 8. An apparatus according to any of thepreceding claims, further comprising locking means (18) for temporarilylocking each of the vertical rods (6) in a vertical position.
 9. Anapparatus according to claim 8, wherein the locking means (18) areconnected to the mantles (14) and are displaced together therewith. 10.An apparatus according to any of the preceding claims, furthercomprising knee supporting means (8) arranged to support the front sideof both legs of the user (2) near an upper end of the shanks, the kneesupporting means (8) being arranged to follow the movements of the user(2) in the frontal plane as well as in the sagittal plane.
 11. Anapparatus according to claim 10, wherein the knee support means (8) arecompliant.
 12. An apparatus according to claim 11, wherein thecompliance of the knee supporting means (8) is adjustable.
 13. Anapparatus according to any of the preceding claims, further comprisingsensor means (19, 20, 21) for measuring the inclination of in thefrontal plane as well as in the sagittal plane of the vertical rods (6)and producing an output accordingly.
 14. A balance training apparatus(1) comprising two vertical supportive rods (6), each connected at alower end to a base (3) by a joint (4) having two degrees of freedom, abracing means (8) suitable for supporting the pelvis of a user (2)standing between the two vertical supporting rods (6), the bracing means(8) being connected to an upper end of each of the vertical supportiverods (6) by a joint (5) having one degree of freedom allowing mutualmovement between the bracing means (8) and the vertical rods (6) in theplane of the two vertical rods (6), biasing means (12) for biasing theuser (2) towards an upright position when deviating therefrom in afrontal plane as well as in a sagittal plane of the user (2),characterised in that the apparatus (1) further comprises compliant kneesupporting means (8) arranged to support the front side of both legs ofthe user (2) near an upper end of the shanks, the knee supporting means(8) being arranged to follow the movements of the user (2) in thefrontal plane as well as in the sagittal plane.
 15. An apparatusaccording to claim 14, wherein the compliance of the knee supportingmeans (8) is adjustable.
 16. An apparatus according to claim 14 or 15,wherein the knee supporting means (8) are connected to at least one ofthe vertical rods (6).